Large scale synthesis of highly crystallized SnO₂ quantum dots at room temperature and their high electrochemical performance.

In this work, SnO2 quantum dots with high crystallinity were synthesized on a large scale under mild reaction conditions via an epoxide precipitation route. The SnO intermediate, which was produced in the reactions between epoxide and [Sn(H2O)6](2+), was converted to SnO2 quantum dots by the oxidation of H2O2. It is believed that the protonation and the following ring opening of epoxide promoted the hydrolysis and condensation of [Sn(H2O)6](2+) to form the intermediate. The obtained quantum dots had a maximum specific capacitance of 204.4 F g(-1) at a scan rate of 5 mV s(-1) in 1 mol l(-1) KOH aqueous solution. The electrochemical measurements proved that this high specific capacitance of SnO2 resulted from the Faradaic reactions between SnO2 and the electrolyte. This demonstrates for the first time that SnO2 can be used as a pseudocapacitive electrode material.